JP-A-59-109420(1984) discloses an air conditioner for a motor vehicle in which the air flow passage from a heater core is divided into three subpassages, into each of which a damper (hereinafter called an air mix door) for adjusting the mixture ratio of cool air and warm air is disposed, and the upper blow-out air temperature is adjusted by the right and left air mix doors independent from the lower blow-out air temperature which is adjusted by the center air mix door.
In the above air conditioner the blow-out air division among upper and lower blow-out ports during the bi-level operation mode, in other words ventilation (hereinafter called vent) and floor blow-out mode, differs from that during the heater mode, in other words in the defroster and floor mode, no further individual temperature adjustment from the driver and the passenger next to the driver is considered, thereby it is difficult to control the temperature distribution and air current distribution in the cabin comfortable for both the driver and the passenger next to the driver.
Further, in the above air conditioner, the respective blow-out ports are arranged perpendicular with respect to the air blow-out direction from the blower thereby the equivalent air quantity division to the respective blow-out ports has to be achieved by changing the division ratio of the respective conditioned air passages, as a result the air flow resistance therethrough is increased to cause large noises.
JP-A-55-51615 (1980) discloses an air conditioner for a motor vehicle in which a plurality of temperature conditioned air flow passages are formed and each of which is provided with predetermined blow-out ports.
In the above air conditioner, blow-out temperatures in three levels can be obtained depending upon the blow-out port positions however no individual adjustment is considered with respect to the temperature and air current distribution at right and left sides in the cabin in response to the environmental thermal load condition so that there is a problem that the blow-out temperature can not be controlled properly.
JP-A-58-22710 (1983) discloses an air conditioner for a motor vehicle in which conditioned air of which temperature is adjusted by an air mix door is divided and led into a plurality of blow-out ports, a plurality of branched ducts are provided which lead cool air from the upstream of the air mix door to mix with the conditioned air in the respective blow-out ports and a distributing valve which adjusts the mixture ratio of the cool air into the conditioned air is provided at each opening portion of the branched ducts, thereby the temperature of the conditioned air blown-out from the respective blow-out ports is individually adjusted.
However, in the above air conditioner, only the cool air from the upstream of the air mix door are mixed with the conditioned air, it is impossible to blow-out air with a higher temperature than that of the conditioned air. For this reason, when the air temperature from one blow-out port, for example from the blow-out port of the right side vent is desired to be higher than that of the conditioned air temperature of the conditioned air, the right side vent temperature has to be raised through the actuation of the air mix door, and in this instance, air temperature from the other blow-out ports such as from the center vent and left side vent rises. Accordingly, even if thereafter the amount of cool air is increased through the actuation of the corresponding distributing values in order to resume the original air temperature, a temporary temperature rise can not be avoided, as a result, the air temperature blowing out respectively from the center vent, right side vent and left side vent can not be accurately and individually controlled. Further, there is a problem that the control for the temperature adjustment is complex because the air mix door as well as many distributing valves have to be controlled. Still further, long and complexed branched ducts are required for conveying the cool air to the respective blow-out ports.